Method of fabricating semiconductor device

Abstract

A method of fabricating a semiconductor device according to an embodiment of the present invention includes: forming a film to be processed having a first film thickness on a semiconductor substrate; forming a region, within the film to be processed, having a second film thickness thinner than the first film thickness by processing a part of the film to be processed; processing the film to be processed having the region of the second film thickness formed therein by utilizing a dry etching method while a change in characteristic value of a plasma is monitored; detecting a first timing at which a member right under the region, within the film to be processed, which had the second film thickness before the processing performed by utilizing the dry etching method begins to be exposed in accordance with the change in characteristic value of the plasma during the processing performed by utilizing the dry etching method; and estimating a second timing right before a member right under a region, of the film to be processed, which had the first film thickness before the processing performed by utilizing the dry etching method begins to be exposed in accordance with the first timing, and changing an etching condition for the dry etching over to another one at the second timing.

1 . A method of fabricating a semiconductor device, comprising:
 forming a film to be processed having a first film thickness on a semiconductor substrate;   forming a region, within the film to be processed, having a second film thickness thinner than the first film thickness by processing a part of the film to be processed;   processing the film to be processed having the region of the second film thickness formed therein by utilizing a dry etching method while a change in characteristic value of a plasma is monitored;   detecting a first timing at which a member right under the region, within the film to be processed, which had the second film thickness before the processing performed by utilizing the dry etching method begins to be exposed in accordance with the change in characteristic value of the plasma during the processing performed by utilizing the dry etching method; and   estimating a second timing right before a member right under a region, of the film to be processed, which had the first film thickness before the processing performed by utilizing the dry etching method begins to be exposed in accordance with the first timing, and changing an etching condition for the dry etching over to another one at the second timing.   
   
   
       2 . The method of fabricating a semiconductor device according to  claim 1 , wherein the second film thickness of the film to be processed ranges from 70% to 90% of the first film thickness. 
   
   
       3 . The method of fabricating a semiconductor device according to  claim 1 , wherein estimating the second timing comprises:
 measuring the second film thickness of the film to be processed;   calculating an etching rate in accordance with the second film thickness of the film to be processed, and the first timing; and   obtaining the second timing in accordance with the first film thickness of the film to be processed, the first timing, and the etching rate.   
   
   
       4 . The method of fabricating a semiconductor device according to  claim 1 , wherein the characteristic value of the plasma is either an emission intensity or impedance of the plasma. 
   
   
       5 . The method of fabricating a semiconductor device according to  claim 1 , wherein the etching condition for the dry etching for the film to be processed is changed at the second timing to another one that an etching selectivity between the film to be processed and the semiconductor substrate is made larger than that of the former etching condition. 
   
   
       6 . The method of fabricating a semiconductor device according to  claim 5 , wherein the dry etching for the film to be processed is performed by using a fluorocarbon system gas, and the etching condition for the dry etching for the film to be processed is changed at the second timing to another one that a C/F ratio of the fluorocarbon system gas is made larger than that of the fluorocarbon system gas of the former etching condition. 
   
   
       7 . The method of fabricating a semiconductor device according to  claim 1 , wherein the film to be processed is a silicon oxide film, and the dry etching is performed by using a gas containing therein F. 
   
   
       8 . The method of fabricating a semiconductor device according to  claim 7 , wherein the gas containing therein F is a fluorocarbon system gas. 
   
   
       9 . The method of fabricating a semiconductor device according to  claim 1 , wherein the film to be processed is a silicon nitride film, and the dry etching is performed by using a fluorocarbon system gas. 
   
   
       10 . The method of fabricating a semiconductor device according to  claim 1 , wherein the film to be processed is an organic film, and the dry etching is performed by using at least one of a gas containing therein O, a gas containing therein N, and a gas containing therein H. 
   
   
       11 . A method of fabricating a semiconductor device, comprising:
 forming a gate electrode on a semiconductor substrate through a gate insulating film;   forming a film to be processed having a first film thickness on the semiconductor substrate, and an upper surface and a side surface of the gate electrode;   applying an organic film onto the film to be processed;   etching back the organic film by utilizing a dry etching method until a portion of the film to be processed overlying the upper surface of the gate electrode is exposed;   thinning the exposed portion of the film to be processed overlying the upper surface of the gate electrode by utilizing a dry etching method until the exposed portion of the film to be processed has a second film thickness;   removing the organic film by utilizing an ashing technique after thinning the exposed portion of the film to be processed overlying the upper surface of the gate electrode by utilizing the dry etching method;   processing the film to be processed by utilizing a dry etching method while a change in characteristic value of a plasma is monitored after removing the organic film by utilizing the ashing technique;   detecting a first timing at which the gate electrode begins to be exposed in accordance with the change in characteristic value of the plasma;   estimating a second timing right before the semiconductor substrate begins to be exposed in accordance with the first timing, and changing an etching condition for the dry etching over to another one at the second timing; and   removing the film to be processed overlying the semiconductor substrate, thereby leaving the film to be processed on the side surface of the gate electrode.   
   
   
       12 . The method of fabricating a semiconductor device according to  claim 11 , wherein the second film thickness of the film to be processed ranges from 70% to 90% of the first film thickness. 
   
   
       13 . The method of fabricating a semiconductor device according to  claim 11 , wherein estimating the second timing comprises:
 measuring the second film thickness of the film to be processed;   calculating an etching rate in accordance with the second film thickness of the film to be processed, and the first timing; and   obtaining the second timing in accordance with the first film thickness of the film to be processed, the first timing, and the etching rate.   
   
   
       14 . The method of fabricating a semiconductor device according to  claim 11 , wherein the characteristic value of the plasma is either an emission intensity or impedance of the plasma. 
   
   
       15 . The method of fabricating a semiconductor device according to  claim 11 , wherein the etching condition for the dry etching for the film to be processed is changed at the second timing to another one that an etching selectivity between the film to be processed and the semiconductor substrate is made larger than that of the former etching condition. 
   
   
       16 . The method of fabricating a semiconductor device according to  claim 15 , wherein the dry etching for the film to be processed is performed by using a fluorocarbon system gas, and the etching condition for the dry etching for the film to be processed is changed at the second timing to another one that a C/F ratio of the fluorocarbon system gas is made larger than that of the fluorocarbon system gas of the former etching condition. 
   
   
       17 . The method of fabricating a semiconductor device according to  claim 11 , wherein the film to be processed is a silicon oxide film, and the dry etching for the film to be processed is performed by using a fluorocarbon system gas. 
   
   
       18 . The method of fabricating a semiconductor device according to  claim 11 , wherein the film to be processed is a silicon nitride film, and the dry etching for the film to be processed is performed by using a fluorocarbon system gas. 
   
   
       19 . The method of fabricating a semiconductor device according to  claim 11 , wherein each of the dry etching and the ashing for the organic film is performed by using an O 2  gas, and the dry etching for the film to be processed is performed by using a fluorocarbon system gas. 
   
   
       20 . The method of fabricating a semiconductor device according to  claim 11 , wherein etching back the organic film, thinning the exposed portion of the film to be processed overlying the upper surface of the gate electrode by utilizing the dry etching method, removing the organic film by utilizing the ashing technique, processing the film to be processed by utilizing the dry etching method, and removing the film to be processed overlying the semiconductor substrate, thereby leaving the film to be processed on the side surface of the gate electrode are carried out in the same chamber.